Pallets for warehousing use and material handling typically have been constructed of wood and provided in a permanent structure. Pallets generally have one or two decks and are provided in 2-way entry or 4-way entry types.
Wooden pallets although used almost universally in material handling suffer from considerable drawbacks. In view of the permanence of the structure, wooden pallets occupy considerable storage area during shipping from the manufacturer to the consumer and when not in use. Wooden pallets cannot be stored out-of-doors as moisture is readily absorbed, increasing its weight, altering its dimension, promoting fungal and bacterial growth, and leading to degradation of the material on prolonged exposure. The bulk size and the necessity to store wooden pallets in a sheltered area gives rise to considerable shipping and storage costs.
Further, wooden pallets typically are quite heavy and can be used only with considerable difficulty in certain industries, such as the food industry, in which cleanliness and corrosion resistance are essential. Effective sterilization of wooden pallets is extremely difficult.
Construction of pallets from wood constitutes a potential fire hazard due to the ready flammability of wood.
Damaged wooden pallets generally are not repairable and represent a considerable disposal problem. Reclamation of the wood generally is not practical or feasible due to the various nails, screws or other fasteners used in the construction and the damaged pallets have to be disposed of by burning or as land-fill. The former manner of disposal generally is impractical, due to air pollution control requirements, and the latter manner is expensive, both in terms of haulage costs to a suitable dump and space occupied at the land-fill.
Further, wooden pallets generally are not readily color-keyed for various uses, since suitable paints for this purpose either lack the strength to withstand extensive use and hence are easily removed during use of the pallets, or are so expensive as to be prohibitive.
In view of these difficulties, attempts have been made to use other construction materials for the provision of pallets, typically plastics. However, plastic pallets suffer from several drawbacks, such as, the plastic materials involved are quite expensive, the pallets must be molded as a single unit again giving rise to a bulk size problem, a minor crack in the structure is sufficient to seriously impair the strength of the pallet, the pallets are severely affected by extremes of temperature, the plastic generally is degraded by exposure to sunlight, and damaged pallets are difficult to dispose of economically.